Explosive testing apparatus



Oct. l0, 1950 P. DE JARLAls EXPLOSIVE TESTING APPARATUS 3 Sheets-Sheet l Filed Jan. 20, 1945 Oct. 10, 1950 P. DE JARLAls vEXPLOSIIVE TESTING APPARATUS 3 Sheets-Sheet 2 Filed Jan. 20. 1945 /NvENToR Pff/L if DE JAR/.A ls

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3 Sheets-Sheet 3 P. DE JARLAIS EXPLOSIVE TESTING APPARATUS mad Jan. 2o, 1945 Patented Oct. l0, 1950 UNITED STATES PATENT oFI-'Ic 2,525,020 ExrLosivE TEs'rmG APPARATUS Philip De Jamie, champun, Minn., minor to Federal Cartridge Corporation, Minneapolis, Minn., a corporation oi Minnesota Application January 20, 1945, Serial No. 573,763

(ci. 'za-ss) 3'Claims. 1

This invention relates to apparatus for testing explosives for uniformity of explosive power, and particularly to the testing of primers or small arms ammunition. In testing primers for unlformity of performance, a selected number of samples are fired. Heretofore the only tests available have been whether or not the primer fired at all with a given hammer pressure on the firing pin. In accordance with the present invention there is provided a means for testing not only for the existence of the primer exp1osion but also the degree of primer explosion or flash" that occurs.

It is an object of the present invention to provide means for testing explosives of the character described to determine the amount of explosive force as indicated by the flash of the explosion. It is a further object of the invention to provide an improved primer testing apparatus capable of visually indicating the amount of primer ilashJ It is also an object of the invention to provide a photo-electric apparatus capable of indicating the primer flash and of providingr a sustained indication by which the degree of explosion or flash is visually indicated and the indication sustained until manually reset. It is a further object of the invention to provide improved photo-electric amplifying and indicating apparatus of specific and general utility and to provide an improved explosive testing apparatus and adjuncts thereto.

The invention is illustrated with reference to the drawings in which Figures 1A and 1B taken together are a wiring diagram of the electrical apparatus of the present invention;

Figure 2 is a front elevational view, partly in section, of the explosion testing apparatus and chamber;

Figure 3 is a side elevational view, partly in section, of the apparatus of Figure 2;

Figure 4 is a plan view, partly in section, of the apparatus of Figure 2; and

Figure 5 is an enlarged fragmentary sectional view of a portion of the ring pin mechanism used in the apparatus of Figure 2.

Throughout the drawings corresponding numerals denote identical parts. l

While the invention is of general utility and may be utilized for the testing of ammunition of various sizes, the apparatus illustrated herein is constructed for the specific (yet illustrative) purpose of testing primer cups used in small arms ammunition such as shotgun shells, rie bullets and the like.

Referring to Figures 2-5 there is illustrated a table or mounting board, generally designated I0 which is provided with a cutout at II to receive the top plate I2 of a container generally designated I3 into which the primers are fired. The container is of rectangular configuration as herein illustrated, but may be of any suitable or convenient shape. It is provided with side Walls I4 and I5, a back wall I6 and a front wall Il. A flanged bottoml cover 20 is fastened to the side walls by means of screws 2| and is provided at itsleft end, as shown in Figure 2, with a bottom plate 24 that is held in place by means of wing nuts 25. On the front and back Walls are provided channels 26 and 21 which serve to support a glass partition 29, the partition being likewise supported by ribs 30 on the bottom cover plate 24. In the space 3| between the side wall I5 and the glass partition 29 there is mounted a photocell generally designated 35 positioned in the socket 36, the latter being supported upon insulators 31. Suitable terminals 38 and 39 are provided for the photocell in a well known manner and the lead wires are taken out through grommet 34. At another portion of the Abottom 20 there is provided a vent tube 40 that is connected to an exhaust blower so as to remove the smoke of the explosion from the space 4I between side wall I4 and the glass partition 29. The upper portions of the side and end walls are provided with venting apertures 42 so as to permit air to be drawn through the container to clear the smoke. It will be noted that the venting apertures are located well up on the side and end walls and are thus recessed into the space Il in the table I0. Therefore no light can enter through these holes and accordingly the photocell is not disturbed in its operation. Any suitable light-shielded vents could be used.

Upon the upper part of the plate I2 there is fastened a flanged collar 44 having a female thread 45, the collar 44 being fastened to the i plate I2 by a plurality of screws 46. The plate I2 is provided with a hole 4l and within the collar 44 there is positioned a removable flanged collar 48 that has a ring aperture 49 and has a recess 50 of appropriate size to receive the particular explosive element undergoing testing. The collar 4B may be removed and others inserted for receiving explosives of varying sizes undergoing testing. A conical cap generally designated 52 is threaded at '53 so as to be easily screwed onto the threads 45 of the ilanged collars 44, the outer portion of the cap 52 being knurled at 54 as illustrated in Figure 2 so that it may be removed is internally threaded at 55 to receive the firing pin support 56 that is correspondingly threaded, the latter being held in vertical adjustment by the locking nut V51. It will be noted that the firing pin support 56 may thus be raised and lowered to any position desired so that its bottom will exert firm pressure on the margin of the explosive element 60 undergoing testing. In this instance the explosive is a primer cup used for shotgun shells, and it is held firmly in the recess 50 of the primer cup receiving collar 48. A firing pin is illustrated at 58 and is provided with a round upper surface 59, the pin 58 being fitted neatly so as to have a dry sliding fit in the firing pin support 55.

Upon the rear part of plate l2 there is provided a block 62 which is fastened in place by the cap screws 63. Block 62 serves as a support for the post 64 that has a flat 65 milled off at one place. A side arm 66 is mounted so as to slide up and down on the rod 64 and has a set screw 61 that abuts against the flat 65, thus accurately positioning the arm 66. The entire rod 64 is mounted for rotation and hence adjustment in the block 62 and is held by means of a set screw 68.

At the forward end of the arm' 66 there is mounted an electromagnet 69 having a core 10 provided with a small fiat area 1| at the bottom which serves centrally to locate the steel ball 12 which is suspended magnetically. Suitable wiring connections for the magnet 69 are provided by lines which are connected through switch 16 to a source of direct current at 80. So long as switch 16 is closed magnet 69 is energized and serves to suspend the ba 12. The post 64 and side arm 66 are adjuste mediately above the firing pin 58, and the side arm 66 may be adjusted vertically so that the ball drops through a uniform vertical distance and thus applies a uniform striking pressure to the firing pin. When the switch 16 is opened the magnet 69 is de-energized, the ball 12 falls through a uniform distance striking the pin 58 and thus applies a uniform firing pressure to the primer or other explosive 60 undergoing testing.

The explosive therefore fires into the space 4| of the testing chamber I3 and the illumination or fiash caused by the explosion passes through the glass partition 29 and falls upon the elements of the photocell. The degree of fiash has been discovered to be indicative of the amount of explosion produced by the primer or other explosive, and the variation in electrical constants of the photocell thus serves as a signal impulse which through suitable amplification yis then recorded or indicated as the performance characteristic of the explosive undergoing testing. vCover 24 may be removed and the glass partition 29 is wiped off from time to time so that no variable factor is introduced due to smoke-clouding of. the glass. The interior of the casing I3 is painted a dull black and is likewise cleaned when occasion requires so that reflected light is likewise maintained at a minimum.

Referring to Figures 1A and 1B, by locating these drawings with Figure 1B at the left and Figure 1A at the right, there is provided a composite wiring diagram of the electrical apparatus of the invention.

In the lower part of diagram Figure 1B, opposite the bracket 8| is a power supply serving the amplifier illustrated under the bracket 82, the photocell which serves as the input of the amplifier being illustrated at 35. Power is supplied so that the ball is im-v by alternating current lines L1 and Ip' and is controlled by a suitable switch 83 and fuse 84 to feed lines Li and L2 which then serve as supply bus bars to the entire apparatus. Lines L1 and Lz are connected to the primary 86 of a transformer generally designated 81, the transformer being provided with a low voltage secondary 88 that serves as the power supply for the filament 89 of a full-wave rectifier tube 90. The plate supply of rectifier tube 90 is provided by the high voltage secondary 9| of the transformer, terminal 92 thereof being connected to anode 93 and terminal 95 to anode 94. The mid-point of winding 9| is connected through junction 96 and line |01 to junction |08 and thence via line |01 to terminals |09 and ||0 which are negative output. From filament 89 line ||4 extends through junction ||5 and inductance ||6 to junction 98, thence through line |00, terminals |0| and |02 to terminal |03 which is positive output. The potentiometer resistor |05 is connected across terminals ||3 and |03. A pair of voltage regulator tubes ||8 are connected in series through resistor 9 from junction |08 on line |01 to junction |0| on line |00. The condenser 91, inductance ||6 and voltage regulator tubes I8 serve to stabilize and remove substantially all ripple from the output of rectifier 90 in a well known manner. A third secondary |20 on transformer 81 supplies leads X--X which serve as filament supply to the filaments of the amplifier shown under thebrackct 82 as hereinafter described.

Junction |02 on line |00 is connected through line |2|, resistor |22, line |23 and resistor |24 to junction ||0 and the latter is connected through condenser |34 to ground |35. Intermediate tap |25 of resistor |24 is of positive potential and is connected through line |26 to the anode |21 of the photocell 35, and from the cathode |28 of the photocell line |29 extends through junction |30 and resistor |3| to zero potential at terminal ||3.

The first stage of amplification is a multiple grid, indirectly heated amplifier tube |31 having filament heater |38, cathode |39, a first grid |40,

, vsecond and third grids |4| and an anode |42.

The filament heater |38 is connected to power supply X-X as previously indicated and the cathode |39 is connected to junction |44 and thence through resistor |45, junction |46 and line |41 to zero potential terminal ||3. Grid |40 is connected through line |48, to terminal 30 on the photocell cathode line |29 which thus forms the input. Grids |4| are connected together and are externally connected at |49 to the lead |50 extending from the anode |42 to a variable tap |52 on the potentiometer resistor |05.

The second stage of amplification is likewise a multiple grid, indirectly heated cathode tube generally designated |54 which may conveniently be of the same style as used in the first stage. The tube |54 is provided with a cathode heater |55, cathode 56, first grid |51, second and third grids |58 and anode |59. The cathode heater or filament is connected to terminals X-X of the transformer secondary |20, and cathode |56 is connected through junction |60, resistor |6|, and line |62 to terminal |46. The first grid |51 of the second stage is connected through line |63 to terminal |44. The second and third grids |58 are connected together externally at |64 to the anode lead |65, the latter extending to the tl'iable tap |61 on the potentiometer resistor `ionic tube generally designated having cathode heater lament |1|, a cathode |12, a first i' grid |13, a second grid |14 and an anode |15.

The cathode heater filament |1| is connected to terminals of transformer secondary |20, the cathode |12 being connected-through line |16 to variable tap |11 of the potentiometer resistor |06. The first vgrid |13 is connected through line |18 to terminal |60, the second grid |14 being connected through line |19 to the variable tap |80 of potentiometer resistor |05. The anode is connected through line |8|, through junction |82 to the output terminal |85. A resistor |83 is connected from junction |82 to positive supply |03, the latter serving as one terminal of the output, as exemplified by output line |86.

Referring to Figure 1A, in the lower part of the wiring diagram over the bracketv |88 there is illustrated a bias voltage supply, while over the bracket I 89 there is illustrated the indicator voltage supply. A time delay circuit for a purpose to be described is illustrated at the left of bracket |81. The indicator, which in this instance comprises a plurality of pilot lights each served by a grid controlled glow tube, is generally illustrated under the bracket |90. Input line |85 is connected to junction |9| and thence to junction |92 which is grounded as illustrated at |93. Input line |86 serves to supply a transient positive signal volta/ge. Its connection to the indicator apparatus will be described subsequently.

The bias voltage supply is provided by a transformer, rectier, filter and voltage control system and includes supply lines L1 and Lz (from Figure 1B) that are connected to the primary |94 of the transformer generally designated |95. The low voltage secondary |96 is connected to the lament |91 of a full-wave rectifier tube |98. Transformer secondary |99 has one terminal connected through line 200 to one of the anodes 20| of the rectifier, the other terminal of the transformer being connected through line 202 to the other anode 203. The intermediate tap 208 of the winding |99 is connected through line 204 and serves as one of the output terminals of the rectifier, the opposite output being via line 205 from the rectifier cathode. A pair of condensers 206 and an inductance 201 serve to smooth out the direct current output of the rectifier and a voltage regulator tube 209 and variable voltage regulating resistor 2 0 are provided so that a uniform direct current voltage is supplied the terminals 2|| and2l2.

Referring now to the indicator voltage supply, alternating current is supplied to lines L1 and La, the latter being grounded at |93 as shown. Line L; is connected through junction 2|3 to one ter- .ninal of the primary 2|4 of transformer 2|5, Line L2 being connected through junction 2|6 and junction 2|1 to the opposite terminal of the primary 2|4. The secondary 2|8 of the transformer is connected to the filament 2|9 of a halfwave rectifier tube 220, the anode 22| of said tube being connected through line 222 and through relay contacts RL-l to junction 2|3 on line L1. 4From the mid-point 223 of the transformer seciidary 2 I 8 output line 224 extends through junction 225 and inductance 226 to junction 221. The inductance 226 has a resistor 238 connected in parallel with it. From junction 221 line 228 extends through junctions 229 and 230, and thence through line 23|, thence through the normally closed reset switch 234 and to line 235, the latter being connected in parallel through -all of the signal lamps hereinafter described. From junction 2|1, line 2|8 extends through junctions 236, 231 and 238 to terminal 239 hereinafter referred to. \Condensers 240 and 24|, respectively, are connected between junctions 22S-236 and 221-231 and they serve together with the inductance 226 `and resistor 238 to smooth out the direct current output from rectifier tube 220. A resistor 242 is connected across junctions 230-238 and is provided with a variable tap 243 connected to junction 229 by which the value of this resistor may be varied. From junction 2 I3 on supply line L1 under transformer 2|5, line 245 extends to the cathode 241 of the thermionic tube 248. The tube 248 is provided with a filament heater 249 that is connected. through supply lines Z-Z to the correspondingly numbered terminals Z-Z of the secondary 250 on transformer |95 of the bias voltage supply. The grid 25| of tube 248 and the anode 252 are connected together and are connected through line 253 and junction 254 to the winding of relay RL, the latter being bridged by a condenser 255 connected across its terminals 254 and 239.

Lines L1 and L2 are connected to the primary 256 of a transformer 258, secondary 259 of which serves to supply power to terminals Y-Y, one terminal being grounded through line 256 that is connected to line L2 as indicated. 'I'he termin ls Y-Y serve to supply power to the filaments the indicator tubes hereinafter referred to.

From the bias voltage positive terminal 2||, previously referred to, there extends line 260 that is connected through junction 26| to junction |9| on the input line |85. From junction 26| there is a connection through resistor 26-2 to junction 263. Resistor 262 is shorted by a line from junction 263 to variable tap 264 so that a portion of the resistor may be bridged out, thereby varying its circuit value.

From junction 263 there extends a circuit through a plurality of resistors 265-213 connected in series and terminating vat junction 213 which is. connected through line 215 to the bias voltage negative terminal 2 l2, previously referred to. ,The resistors 262 and 265-213 form a potentiometer which is supplied with a direct current voltage by the bias voltage supply circuit (terminals 2| |-2 l2). The values of resistors 262 and 265-213 determine the voltages applied at junction 63 and junctions 26-5'-213. The resistor 262 and resistors 265-213 may be of uniform value or may be of any desired value so as to establish selected potentials at the various junctions. In an exemplary installation resistor 262 is of 5000 ohms value with a tap at 2250 ohms while resistors 265-213 are of 500 ohms each.

The resistors 262 and 265-213 thus establish a definite potential at junctions 263 and 265-213', grading from a slight negative value at junction 263 to more negative values for each successive junction 265' through 213. These junctions 'thus establish the normally negative potentials of the grids of tubes 29|-300 (Thyratrons) as hereinafter described. In'some instances it is desirable to have unevenly graded potentials at junctions 263 and 26-5'-213' so as to provide a very fine calibration at certain portions of the voltage scale while allowing a coarse calibration at other portions of the scale.

The indicators (tubes 29|-300 and their associated pilot lamps) are all connected in parallel and are identical. Thus, from terminal 263 a circuit extends through resistor 216 to junction 211, and thence through a condenser 218 to terminal 219 on the input line |86, junction 211 being connected to the grid 288. Tube 29| has a filament 282 that is supplied with power from transformer secondary terminals Y-Y of transformer 258. The anode 284 of the grid controlled glow tube is connected through a pilot lamp 285 to the line 235 which extends back through the normally closed reset switch 234 to the indicator voltage supply as previously described.

The transient signal voltage incoming on line |86 is positive in value and is impressed through condenser 218 upon junction 211 and hence upon grid 288. The potential of grid 280 is thus caused to shift in the positive direction and depending upon the magnitude of the transient positive voltage incoming signal. Where this positive signal is of suiiicient magnitude it causes a discharge to take place between the cathode 282 to anode 284 and a circuit is thus established to signal lamp 285. Once started, tube 29| continues to conduct until its cathode-anode circuit is interrupted.

The remaining grid controlled glow discharge tubes 292-300 (or more if they are employed), are connected similarly, except that the grid potential normally applied on each successive tube is higher than the grid potential applied on its lower numbered neighbor and therefore an incoming signal must have a greater positive value to initiate discharge in tube 292 than is required to initiate discharge in 29|. Similarly, an incoming signal must have a greater value to discharge tube 293 than is required to discharge tube 29| and tube 292.

Assuming that the incoming signal wave is of sufficient positive value, the potential applied to all of the grids may be sufiicient to initiate current flow through any given sequence of tubes beginning at tube 29| and continuing through successive tubes to any stopping point up to the last tube 300. The tubes thus rendered conductive begin to discharge and their corresponding signal lamps are energized. Thus, the number of tubes that discharge indicates the magnitude of the incoming signal wave.

Operation In order to initiate operation the switch 83 is f closed thus establishing a circuit from line L1 to Line L1. Lilies L1 and L2 thus being energized excite transformers 81, |95, 2I5 and 258. When transformer 81 is energized it causes the operation of the rectifier circuit, thus establishing a potential across the vpotentiometer resistor |85, and the amplifier under the bracket 82 is energized. A potential gradient is likewise established across resistor |24, and since the anode of the photocell is connected to tap |25, a positive voltage is impressed across the cell and through resistor |3| to terminal 3. When the explosive cartridge 68 undergoing testing is fired a fiash occurs in the container I3 and light thus falls upon the photocell 35 causing a discharge to take place from the cathode to the anode. This input signal is impressed upon grid |40 of the first stage amplifier tube |31 and the signal is amplified through tubes |54 and |18 in a well known manner and is impressed across resistor |83 at terminals |82 and |03, the signal being communicated through lines |85 and |86 to the indicator apparatus shown in Figure 1A. The signal voltage on line |86, however, will not be effective to operate the indicator until a predetermined time has initially elapsed after the switch 83 has been closed to energize the system. This time delay is provided so as to prevent the indicator gridl controlled glow discharge tubes 29 |-300 from being caused to discharge before the filaments of these tubes have heated to an operating temperature. The time delay is provided as follows:

When switch 83 is closed and lines L1 and Lz are thus energized, this energizes the primary |94 of transformer |95 and secondary 250 which accordingly causes the filament of the time delay tube 248 to be energized. After a predetermined interval this tube becomes conductive and a circuit is established from line L1 (at the indicator voltage supply |89) to junction 2|3 and thence through line 245, tube 248 which is then conductive, line 253, the coil RL of the time delay relay to line 2|8,fto junction 2|1 on line Lz. Relay RL is thus energized and closes its contacts RL-I in the plate circuit of the indicator voltage supply tube 220. Until this has occurred the indicator tubes 29|-300 cannot discharge regardless of the signal impressed upon its grids. Assuming then that the input signal voltage on line |88 occurs after relay RL has actuated this positive signal voltage is impressed upon condenser 218 of tube 29| of the indicator apparatus and through each ,of the parallel condensers to thegridsvof the tubes 292-388 The signal voltage is thus appliedr to the grids of vall of the tubes, and depending upon the magnitude of the positive signal voltage will cause one or more successive tubes (beginning at tube 29| and reading to the right) to become conductive. When this occurs a circuity is established from the cathode 282 to the anode 284 of tube 29| and from the cathode to the anode of eachv of the tubes as has been energized by the positive signal impressed upon it. Assuming, for example, that tubes 29|-293 thus are energized a circuit is established from line L1 at the indicator voltage supply through the thenA closed contacts RL-I of the time delay relay through line 222 to the anode 22| of tube 220. and thence to the cathode 2|9 from which a circuit continues to the, center point of transformer -winding 2|3 and thence over line 224, inductance 228, line 228, through the normally closed reset switch 234 and line 235 to the signal lamps corresponding to the glow discharge tubes `29|-293, thence in parallel through these signal lamps and through the glow discharge tubes which are then conductive and through the filament circuit Y-Y of the filament transformer ground connection 256 to junction 2| 8 online Lz. therefore energized 'and remain energized until the reset switch`234-ispushed so as to open this circuit andl re-establish non-conductive conditions in' the grid controlled thermionic tubes 29|-283. r

In the event a smaller or larger positive voltagel is received online |86 a lesser or greater number of tubes 29|-380 are operated along the signal lamps lcorresponding to them. In this manner the degree of "iiash produced by the explosive undergoing testing is readily indicated rand the indication is maintained for a period of time sufficient to make any desired recorded notation of the result.

Many variations may be made in the apparatus without departing from the spirit of the invention. Thus, the container I3 and apparatus mounted on it may be enlarged sufficiently to take full size explosives such as shotgun shell cartridges, 22 caliber cartridges or rifie cartridges of The signal lamps are larger caliber and the flash of the explosive produced thereby readily measured in the apparatus. Any suitable triggering apparatus may be substituted for the magnet 69 and ball 12 as illustrated. The ball and magnet arrangement provides an exceptionally uniform method of applying firing pin pressure and is especially useful for the testing of percussion caps of all sorts.

For the indicating instrument there may likewise be substituted any desired maximum-reading indicator capable of maintaining indication corresponding to the signal voltage. In some instances it is feasible to eliminate the pilot lamps 285, etc. since the glow discharge tubes may readily be mounted in a convenient position such that the light therefrom is visible to the operator. These and other variations will be apparent to those skilled in the art and are within the purview of the invention herein illustrated, described and claimed.

What I claim is:

1. An apparatus for testing explosive charges comprising a container, a photocell mounted in the container so as to be normally dark, means for exploding the charge into the container in a direction so that the light flash therefrom illuminates the photocell, amplifier means connected to the cell for providing a positive signal voltage which is a function of the light falling upon the cell, a plurality of grid controlled glow tubes each having an input circuit and a cathode and anode therein and having their grids normally biased negatively in progressively greater amounts from tube to tube, and means for applying the amplifier positive signal voltage upon the grids of said tubes to operate one or more of them depending upon the amount of said positive signal voltage.

2. The apparatus of claim 1 further characterized in that the output of each of said grid controlled glow tubes is connected to a signal which is operated when the tube is conductive, and means for de-energizing all of said tubes.

3. A photoelectric apparatus comprising a housing, a photocell mounted in the housing so as to be normally dark, said housing being provided with means to hold an explosive charge which may be exploded therein, the photocell being positioned within the housing so that the light flash from said explosion falls upon the photocell, amplifier means connected to the photocell for providing a, positive signal voltage which is a function of the light flash from said explosion falling upon the photocell, a plurality of grid controlled glow tubes each having an output circuit and a, cathode and anode therein and having their grids normally biased negatively in progressively greater amounts from tube to tube, means for applying the amplifier positive signal voltage upon the grids of said tubes to operate one or more of them depending upon the amount of said positive signal voltage, and circuit interrupting means in the output circuits of said tubes for maintaining said output circuit initially open for a period sufficient to allow the cathodes thereof to heat to operating temperature.

PHILIP DE JARLAIS.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,716,775 Hayes June 11, 1929 2,087,598 Hebler July 20, 1937 2,095,124 Cockrell Oct. 5, 1937 2,171,861 McCabe Sept. 5, 1939 2,199,394 Dewan May 7, 1940 2,300,361 Reynolds Oct. 27, 1942 2,323,301 Anderson July 6, 1943 2,402,580 Roters June 25, 1946 FOREIGN PATENTS Number Country Date 12,546 Great Britain 1892 OTHER REFERENCES Book-Marshalls Explosives Publisher J. 8: A. Churchill, London, 1915, pg. 428. 

